This invention relates to an optical control device used as an optical propagation element having active functions such as optical modulation and optical branching.
Heretofore, in the case where light propagating in an optical fiber is modulated or branched, an optical coupler is employed to couple the optical fiber to a wave conducting path.
Since an optical coupler of this type must be high in optical coupling efficiency, it is necessarily delicate in mechanism and intricate in construction. For instance, the thickness of a film-shaped optical wave conducting path used for optical modulation or branching is only several microns (.mu.), and accordingly the requirements for positioning for optical coupling and for end face flatness are considerably severe. Thus, the optical coupler is still disadvantageous in that the optical arrangement is severe and the operation is difficult.